More than a dozen environmental groups in Russia have shuttered their operations since the authorities required them to register as "foreign agents" under a politically charged law that critics say is stymieing civil society and political dissent, a U.S.-based rights group says in a new report.

The November 21 report by Human Rights Watch (HRW) accuses Russian authorities of using the law to "silence some of the country's most effective, rigorous, and committed environmental groups."

"The effects of the law have been devastating for environmental groups and environmental activists, and we do know that a broad range of activities that were working to preserve Russia's natural environment can no longer take place," Richard Pearshouse, HRW's associate environment director and the author of the report, told RFE/RL in a telephone interview.

The release of the report comes five years after the 2012 law came into effect, targeting nongovernmental organizations that receive foreign funding and are deemed to be engaged in "political" activities.

Russian NGOs deemed to meet those criteria are required to register as "foreign agents." Opponents of the law say it is aimed at discrediting independent voices and organizations critical of the authorities, including election monitors and human rights groups -- criticism that officials have brushed off.

The law has also swept up groups engaged in environmental activism and HIV-prevention efforts, and more recently Russian lawmakers have launched a push to label foreign-funded media outlets as "foreign agents" amid a mounting standoff with the United States.

Russia has repeatedly accused the United States and other Western governments of seeking to stoke political unrest in the country by funding nongovernmental organizations, including election monitors and human rights groups often critical of the authorities.

Of the more than 150 NGOs that the Russian Justice Ministry has labeled "foreign agents" since President Vladimir Putin signed the law into force, 29 have been environmental groups, the HRW report says.

It says at least 14 of those environmental organizations have halted their work rather than continue to operate under the "foreign agent" law, whose reporting requirements have been criticized as excessively burdensome for groups that often work on shoestring budgets.

The report adds that the figure could be higher given that representatives of 11 groups either could not be reached or declined to discuss the matter.

The environmental activities that Russian authorities determined to be "political" in nature include assessing the impact of hunting quotas, petitioning for the release of jailed environmental activists, and public campaigning against nuclear-energy plants, mines, refineries, and other industrial facilities, the HRW report says.

It cites the case of Planeta Nadezhd (A Planet of Hope), an NGO based in the city of Ozersk, near the Mayak nuclear complex in the Chelyabinsk region. The group, which has ceased its activities, was active in defending the rights of radiation victims.

The organization's director, Nadezhda Kutepova, left Russia for France in 2015 after the authorities branded it a "foreign agent" and a local television channel accused her group of espionage. She received political asylum in France last year.

The region where the NGO operated is at the center of international attention after Russia's meteorological service said on November 21 that it measured "extremely high" concentrations of the radioactive isotope ruthenium-106 (Ru-106) in the southern Urals in late September.

The statement came after France's nuclear-safety agency said in early November that a nuclear facility either in Russia or Kazakhstan was likely the source of a cloud of radioactive pollution over Europe at the end of September. Neither Kazakhstan nor Russia has acknowledged that any accident occurred.

Pearshouse told RFE/RL that it was difficult to measure the "exact impact of the law in environmental terms."

"But what we do know is that an incredibly useful range of very important environmental work has ceased," he said.